This invention relates generally to blow molding machines and more particularly to a take-out assembly for removing a blown article such as a plastic bottle from a mold assembly on the machine and transferring it to a material-handling conveyer.
Blow molding machines are used to produce various types of articles and have been found to be particularly useful in making plastic bottles containing various types liquids such as cooking oils, beverages, household chemicals, etc. The machines operate by extruding into a mold cavity a parison of plastic material which is heated to a semifluid state, and then is subsequently subjected to internal pressurization through an inserted needle causing the plastic to inflate and conform to the inside surfaces of the mold cavity.
A popular type of blow molding machine includes a rotary wheel or turntable, which rotates about a horizontal axis. The wheel has a number of multi-piece, openable and closeable mold assemblies circumferentially spaced therearound. The wheel is rotated past a number of work stations, at a first work station the mold parts are separated to expose the mold cavity and, as the parts arrive at or pass a discharge nozzle of a plastic extruder, the cavity is charged with the heated plastic parison. That mold assembly is then clamped together and rotated to the next work station where a fluid such as air is injected into the mold to cause the parison charge to expand and conform to the inside configuration of the mold cavity. As the wheel continues to rotate, the mold assembly is cooled, thereby causing the plastic material to solidify. At a final discharge workstation, the mold assembly is opened and the finished plastic bottle is removed by a take-out assembly.
A production capacity is determined by the number of blow mold assemblies located around the circumference of the wheel, the speed of rotation of the wheel, and the rate at which the take-out assembly is capable of removing finished bottles from the rotating wheel.
In the past, take-out assemblies have been of rather complex construction and quite often have been unable to operate fast enough to permit the blow molding wheel to be operated at its maximum production capacity. Thus, the cost of producing the finished plastic articles has been unnecessarily compromised.
The primary object of this invention is to provide a blow molding machine of the rotary wheel type having a plurality of mold assemblies spaced around the circumference thereof, and a take-out assembly located adjacent a discharge station of the rotary wheel, the take-out assembly being of simple, economical, but yet reliable construction capable of operating at a capacity sufficient to enable the rotary wheel to function at its maximum designed production speed.
The novel take-out assembly of the invention accomplishes the above objective by providing a first substantially linear or large radius curved transfer mechanism which removes a finished bottle from a mold assembly at the discharge station of the rotating wheel and transfers that finished bottle upwardly along substantially a straight line to a second separate rotary transfer mechanism which receives the bottle from the first mechanism, rotates the bottle through 1800 into an upright position, and then places the upright bottle onto an exit transfer conveyer. The overall pickup assembly is capable of operating at higher speeds because once a finished bottle is transferred from the first mechanism to the second mechanism, the first mechanism may quickly return to the discharge station of the wheel to pick-up a finished bottle from the next mold assembly presenting itself on the wheel. During the return stroke of the first pick-up mechanism, the second rotary transfer mechanism places the first bottle onto the exit transfer conveyer and subsequently returns to its initial handoff position ready to receive the next bottle from the first linear transfer mechanism.
The novel take-out assembly of the invention has been especially adapted for use with a blow molding machine having an approximately fifty-three inch (53xe2x80x3) pitch diameter wheel with five mold assemblies positioned around the circumference thereof and capable of producing large blown plastic bottles, for example of a two and one half gallon size (4xc2xdxe2x80x3 widexc3x979xe2x80x3 longxc3x9715xe2x80x3 high) or thirty-five pound size (16xe2x80x3 highxc3x979xe2x85x9cxe2x80x3 square) capable of producing about twenty-five bottles per minute (25 bpm). The first linear transfer mechanism moves a finished bottle away from the wheel, so that the wheel may continue to rotate, along substantially a straight line through a distance of about forty-six inches to a handoff station where it is handed off to the second rotary mechanism which rotates on a radius of about twenty-four inches to place the finished bottles on the exit conveyer. Advantageously, the novel take-out mechanism of the invention is capable of operating at at least twenty-five bpm, the maximum capacity of the blow molding wheel.
In operation, as the wheel rotates into the take-out position at the final discharge station, the mold is opened, knockouts in the mold eject the bottle from the mold and place it on the wheel""s centerline ready for pickup. The first linear transfer mechanism picks up the bottle with a combination of vacuum cups and grippers and moves the bottle along a substantially straight line to a handoff station located about three feet upwardly away from the wheel. The first mechanism pulls the bottle out of the way of the wheel so that the wheel may continue to cycle. During the linear transfer of the bottle, the bottle is rotated by a cam, track or actuator (pneumatic cylinder), so that when it reaches the handoff station the bottle is in the proper bottom up vertical orientation ready for handoff. At the handoff station, the second rotary transfer mechanism employs a head assembly with vacuum cups and/or grippers, the head assembly being first extended to grab the bottle from the first mechanism and then slightly retracted so that the first mechanism can repeat the bottle pick up cycle without interference from the second rotary mechanism. The rotary transfer mechanism then rotates the bottle through one hundred and eighty degrees to orient the bottle right side up. The head assembly is then again extended to place the bottle on the linear transfer conveyer. Alternatively, the head assembly may be extended as it is rotated. Subsequently, the head assembly is retracted to clear the conveyer and permit the rotary mechanism to rotate without interference. Operation of the first and second mechanisms is timed so that each is able to operate at sufficient speed and to cooperate with each other so that finished bottles may be removed from the rotary wheel at a speed sufficient to permit the rotary wheel to operate at its maximum designed capacity.
As an added advantageous feature of the novel take-out assembly, the pick up device of the first linear mechanism includes both vacuum cups and mechanical grippers, the vacuum cups normally engaging the finished blown bottle and performing the transfer operation out of the mold to the handoff station. However, if a miss blow occurs the mechanical grippers will still pick up the parison and transfer it out of the mold. At the handoff location, the second rotary transfer mechanism only has vacuum cups that cannot pick up a miss blown pan son. Therefore, when the mechanical grippers of the first mechanism release the parison, the parison is dropped and falls onto a slide which directs the miss blown parison away from the machine without causing any handling or jamming problems of the machine.
These and other objects of the invention will become apparent from reading the following description of the invention wherein reference is made to the accompanying drawings.